1. Field of the Invention
The invention relates to a continuously working heating plate press used in the manufacture of particle boards, fiber boards, plastic boards or the like. More particularly, the invention relates to a plate press comprising endless steel belts which are run around a fixed press table and a lowerable press ram via drive and tail drums, the press table and press ram defining an adjustable press gap. The steel belts transmit pressure to the material drawn moving the material through the press gap. The steel belts are supported by roller bars as they travel through the press, the roller bars having axes of the rotation transverse to the direction of the steel belts. Heating plates are attached to the press table and press ram providing heat to the material in the press gap via the roller bars and steel belts.
2. Description of the Related Art
The heat transfer in known continuously working heating-plate presses have rolling support. However, due to the line contact between the roller bars and the heating plates and the roller bars and the steel belts, the heat transfer is poor as compared to surface contact in cycle-controlled single-daylight presses. Consequently, the continuously working heating-plate press requires an increased use of lubricant to compensate for this disadvantage. The lubricant improves the heat transfer between the roller bars and the heating plates and steel belts in addition to its friction reducing function. The surface ratio of plate presses to rolling support is: EQU surface : line = 100 : 1
However, it should be mentioned as a disadvantage that the quantity of heat that can be transferred (introduced) from the steel belts into the material to be pressed is still not sufficient to shorten the press time to such an extent that a continuous press can be built at an economical and technically still justifiable length. This is because it is known that the length of a continuous press depends on the press time and the yield, required per unit of time, of material to be pressed. A greater yield per unit of time requires a quicker passage and thus a greater press length. A greater press length in turn results in greater friction, larger drive drums, thicker steel belts and thus an inefficiently expensive continuous press.
A further disadvantage of known presses is that a far higher curing temperature is required by today's common binding agents. In addition, shorter curing times are continually being demanded. The required curing temperature of binding agents reacting especially quickly can be around 190.degree. C. and higher. Therefore the material to be pressed, even if already preheated, must still be considerably heated in the hot press. Consequently, due to the limited heat transfer capabilities of existing presses, a larger overall press length or a slower passage (longer press time) through the continuously working press is required to introduce the necessary quantity of heat into the material to be pressed. The higher required curing temperature therefore increases the press time (reducing yield) or requires a considerable increase in the overall length of the press in order to increase yield. Until the pulse of steam for curing the glued particle mat is reached, a longer press distance is thus necessary. However, increasing press length cannot be done economically, which results in a restriction in the output capacity of the press.
The continuously working heating-plate press art lacks a press that can efficiently provide heat energy already within the press to meet the curing temperature requirements of today's binding agents without increasing press time, or increasing press length or reducing required material yield.